Axillary nerve dysfunction
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Axillary nerve dysfunction

Definition

Axillary nerve dysfunction is a loss of movement or sensation of the shoulder because of damage to the axillary nerve.

Causes, incidence, and risk factors

Axillary nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the axillary nerve, which supplies the deltoid muscles of the shoulder. It is not a specific, separate disease, but is caused by many conditions that can damage the axillary nerve.

Dysfunction of a single nerve group, such as the axillary nerve, is called mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage (such as occurs with mononeuritis multiplex).

The usual causes are direct trauma, prolonged external pressure on the nerve, and pressure on the nerve from nearby body structures.

Conditions associated with axillary nerve dysfunction include fracture of the humerus (upper arm bone), pressure from casts or splints, improper use of crutches, intramuscular injections, and shoulder dislocation. Other causes include systemic disorders that cause neuritis (inflammation of nerves).

In some cases, no detectable cause can be identified. Mechanical factors may be complicated by ischemia (a lack of oxygen from decreased blood flow) in the area.

Symptoms

  • Numbness over part of the outer shoulder
  • Shoulder weakness
    • Difficulty lifting objects with the affected arm
    • Difficulty lifting arm above the head

Signs and tests

A neuromuscular examination of the arm and shoulder indicates axillary nerve dysfunction. There may be weakness of the shoulder, with difficulty moving the arm.

The deltoid muscle of the shoulder may show signs of muscle atrophy. A detailed history may be needed to determine the possible cause of the neuropathy.

Tests that reveal axillary nerve dysfunction may include:

  • An EMG (a recording of electrical activity in muscles)
  • A nerve biopsy (may reveal systemic causes for the dysfunction)
  • An MRI to rule out lesions of the cervical spine or nerve roots
Tests are given based on the suspected cause of the dysfunction suggested by the patient's history, symptoms, and pattern of symptom development. They may include various blood tests, x-rays, scans, or other tests.

Treatment

Treatment is aimed at identifying the cause, treating it, and increasing mobility and independence. In some cases, no treatment is required and recovery is spontaneous.

Conservative treatment is given if there is sudden onset of symptoms, minimal sensation or movement changes, no history of trauma to the area, and no evidence of nerve degeneration.

Corticosteroids injected into the area may reduce swelling and pressure on the axillary nerve in some cases. Systemic corticosteroids may be recommended for cases caused by inflammatory lesions (such as brachial amyotrophy and brachial neuritis).

Surgery may be necessary if the disorder is chronic, if symptoms get worse, if there is difficulty with movement, or if tests indicate degeneration of the nerve.

Surgical exploration may be necessary if nerve dysfunction is caused by entrapment, in which case surgical release of the nerve may help.

Surgical removal of tumors or other lesions that press on the nerve may benefit some cases.

Over-the-counter analgesics (such as acetaminophen tablets) or prescription analgesics may be needed to control pain (neuralgia). Other medications (phenytoin, carbamazepine, gabapentin or tricyclic antidepressants such as amitriptyline) may reduce the stabbing pains that some people experience. Whenever possible, medication use should be avoided or reduced to lessen the risk of side effects..

Physical therapy may be helpful to maintain muscle strength. Vocational counseling, occupational therapy, job changes or retraining, or similar interventions may be recommended.

Expectations (prognosis)

If the cause of the axillary nerve dysfunction can be identified and successfully treated, there is a possibility of full recovery. The extent of disability varies. The worst problem most often is shoulder weakness.

Complications

  • Partial or complete shoulder paralysis
  • Partial or complete loss of sensation in the arm (uncommon)
  • Recurrent or unnoticed injury to the arm
  • Deformity of the arm, shoulder contracture or fibrosis (frozen shoulder)

Calling your health care provider

Call for an appointment with your health care provider if symptoms of axillary nerve dysfunction are present. Early diagnosis and treatment increase the chance of controlling symptoms.

Prevention

Preventative measures vary, depending on the cause. Avoid prolonged pressure on the underarm area. Examine casts, splints, and other appliances for proper fit. Crutch training should include instructions not to place pressure on the underarm.

Illustrations

Damaged axillary nerve
Damaged axillary nerve

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Neuropathy - axillary nerve

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